The present invention concerns an apparatus and a method of producing absorbent pads from a flock-air mixture.
In the case of machines for producing absorbent pads as for sanitary napkins, panty liners, disposable diapers or the like, the usual practice is for an absorbent pad or flock core to be formed from a hydrophilic flock mixture on a flock-laying device. The flocks which are required for that purpose are fed to the flock-laying device in the form of a flock-air mixture, being supplied thereto from a disintegrating or pulping device, through a feed conduit.
As the disintegrating device or grinding device converts large amounts of mechanical energy into heat energy while it is in operation, it suffers from a substantial rise in temperature. That fact requires a carrier air flow which is as large as possible from the disintegrating device, to convey the flock-air mixture, whereby that air flow produces the desired effect of dissipating heat from the disintegrating device, and thus affords a cooling action therefor. The comparatively great carrier air flow however entails the disadvantage in the region of the flock-laying device that excessively large amounts of air occur there, and cannot be sufficiently rapidly sucked away by the suction box of the flock-laying device, so that they adversely affect the procedure involved in shaping the suction pads from the flock-air mixture in the flock-laying device.
An object of the present invention is to provide an apparatus for producing absorbent pads from a flock-air mixture in which any excess air in the region of formation of the absorbent pads can be easily removed by a suction effect without adversely affecting the procedure involved in shaping the absorbent pads.
Another object of the present invention is to provide an apparatus for producing absorbent pads from a feed of flock-air mixture through a feed conduit, which provides for a controlled feed of the flock-air mixture to locations in which the respective absorbent pads are formed, thereby enhancing the efficiency of the apparatus.
Still another object of the present invention is to provide a method of producing absorbent pads from a flock-air mixture, which can control a feed of the mixture in such a way as to afford a simple but efficient operating procedure in terms of shaping absorbent pads.
In accordance with the principles of the present invention in the apparatus aspect the foregoing and other objects are attained by an apparatus for producing absorbent pads from a flock-air mixture which is fed through a feed conduit to a shaping recess carrier for forming the respective absorbent pads. The shaping recess carrier rotates in a predetermined direction or circulates in a predetermined circulatory direction. The feed conduit which carries the flow of flock-air mixture has a branching to provide at least first and second conduits. The first conduit is operable to carry a first partial flow of the flock-air mixture and the second conduit is operable to carry a second partial flow of the flock-air mixture. The first and second conduits are directed on to the shaping recess carrier in such positions that the second partial flow through the second conduit meets the shaping recess carrier substantially downstream of the first partial flow through the first conduit in the direction of operating movement of the shaping recess carrier.
Further in accordance with the invention in the method aspect the foregoing and other objects are attained by a method of producing absorbent pads from a flock-air mixture which is fed through a feed conduit to a shaping recess carrier for forming the respective absorbent pads, the carrier rotating in a predetermined direction of rotation or circulating in a predetermined circulatory direction. The flock-air mixture is divided into at least first and second partial flows, the second thereof being directed on to the shaping recess carrier at such a position that it meets the carrier substantially downstream of the first partial flow in the direction of operation of the shaping recess carrier.
It will be noted at this point that the above-mentioned component referred to as the shaping recess carrier may involve for example a rotatable flock-shaping wheel or an endless flock-shaping belt which circulates around guide rollers or a corresponding flock-shaping chain.
The shaping recess carrier is generally a component part of a flock-laying device which, as a further essential component thereof, includes a hollow flock box, with the shaping recess carrier being movable relative to the flock box. In accordance with the invention, at least first and second conduits open into the flock box, each of the conduits carrying a respective partial flow of the flock-air mixture and feeding it to the shaping recess carrier.
The movement of the shaping recess carrier with respect to the flock box means that shaping recesses continuously move into that region in space which is supplied with flock-air mixture from the flock box. The shaping recesses in the shaping recess carrier are initially not yet or scarcely filled with flock so that the sieve-like bottoms of such recesses still involve a comparatively high degree of permeability to the air. It is precisely that fact that the present invention puts to good use insofar as it provides for passing one of the first and second partial flows of the divided flock-air mixture into that region of the flock box in which there are disposed shaping recesses which are filled with flock to an only slight degree and which thus have a sieve-like bottom which still affords good permeability to the air. In that way the suction device of the flock-laying device which sucks the air away from the flock-air mixture to cause flock to be deposited in the respective flock shaping recesses can advantageously suck larger amounts of air out of the flock box, through the bottoms of the shaping recesses which are not yet covered with and thus blocked by flock. In that way the excess air which has been branched away by way of the partial flow can be effectively and efficiently removed from the flock box and at the same time the flock contained in the partial flow in question can be used for producing the respective absorbent pad in the shaping recess.
In accordance with a preferred feature of the invention, the branching of the feed conduit can be such that it produces the first partial flow with a higher volume-specific proportion of flock than the second partial flow and correlatively the second partial flow has a lower volume-specific proportion of flock than the first partial flow. This can still further improve the level of efficiency in terms of removing the air from the apparatus in accordance with the invention. As the second partial flow is directed on to a location of the shaping recess carrier which, as considered in the direction of movement thereof, is substantially downstream of the region of impingement of the first partial flow on to the shaping recess carrier, the shaping recesses which freshly pass into the region of the shaping recess carrier which is covered by the flock box are in this case less rapidly filled with flock and their sieve-like bottoms enjoy a higher degree of permeability to the air, over a longer period of time. As indicated, that in turn permits the excess air to be sucked away in a more efficient manner.
It should be expressly mentioned that, in accordance with the present invention, the partial flows may entail the same volume-specific proportions of flock, as well as different proportions of flock.
In accordance with a further preferred feature of the invention it is possible for three or even more partial flows to be branched off the feed conduit which carries the flock-air mixture. In that situation, it is particularly advantageous for a third conduit to be so directed that the third partial flow carried therein meets the shaping recess carrier substantially upstream of the first partial flow, as considered in the direction of movement of the shaping recess carrier. The first partial flow then passes between the second and third partial flows and it is possible to add thereto a hydrophilic additive, usually a super absorbent polymer, usually referred to as SAP. That additive can be specifically introduced in that way into the region which will constitute the central layer of the absorbent pad in the finished condition. It is thereby securely held in position in the absorbent pad and cannot accidentally come loose from the flock bonding of the absorbent pad.
In order to break up and disperse compacted pieces of flock material or flock lumps within the flock-air mixtures constituting the partial flows, which can occur due to friction with the wall surfaces of the conduits, flow turbulence phenomena as well as static charging, the conduits carrying the partial flows may include pneumatic dispersing devices for dispersing the flock lumps, which are operative to break up and disperse the lumps by accelerating the flock-air mixture of the respective partial flow, together with the flock lumps contained therein, in such a way that the flock lumps are torn apart or burst asunder.
It was surprisingly found that flock lumps which comprise compacted cellulose flocks or fibers can be broken up and dispersed if they are accelerated suddenly with a jerk, jolt or jump by means of a directed flow of fluid, in particular an air flow, of high kinetic energy. In that situation, acceleration and/or fluid friction forces occur, which readily overcome the mechanical and/or electrostatic adhesion forces which are operative between the flocks forming a flock lump. Furthermore, the pneumatic dispersing device according to the invention preferably generates turbulent flows whose acceleration effects which change randomly in respect of direction and magnitude have the result that the flock lumps disintegrate. It has been found to be particularly advantageous in this respect for the flock-air mixture to be accelerated to supersonic speed, preferably to up to twice the speed of sound. Such high speeds ensure that turbulent flow conditions obtain in the dispersing device and the flock-air mixture constituting the respective partial flow is sufficiently accelerated in a jerk-like, jolt-like or jump fashion.
Depending on the respective magnitude of the forces which hold a flock lump together, dispersion of the flock lump occurs at an earlier or later time. A flock lump which is less firmly held together can already be torn apart at the beginning of the acceleration phase whereas a flock lump which is more firmly held together can under some circumstances be destroyed only after the attainment of an adequate degree of turbulence in the flow of the flock-air mixture. At any event the apparatus and the method according to the invention provide that, in contrast to impact arrangements which mechanically break up lumps by the latter impacting against for example fixed bars in a flow conduit, all flock lumps contained in the flock-air mixture flowing through the feed conduit are operatively engaged by the acceleration forces to cause appropriate disintegration and dispersion thereof.
In accordance with a preferred feature of the apparatus of the invention, the pneumatic dispersing device can be arranged in the end region of each of the conduits which carries the partial flows of the flock-air mixture. Preferably, the dispersing device is fitted directly into the opening of the respective conduit into the flock-laying device. The flock-laying device includes a rotating flock-shaping wheel and a stationary flock box into which at least one of the conduits opens by way of the pneumatic dispersing device. The directed jet of the substantially lump-free flock-air mixture which is produced by the pneumatic dispersing device means that it is advantageously possible for that jet to be directed specifically and targetedly in a given direction in space. This means that troughs or shaping recesses provided in the peripheral surface of the flock-shaping wheel, for forming the absorbent pads, can be more effectively filled with flock.
In accordance with another preferred feature of the invention the pneumatic dispersing device can be formed by a nozzle around which the flock-air mixture flows. The nozzle is arranged substantially in the central region of the cross-section of the conduit carrying the respective partial flow. With this configuration of the dispersing device it will be noted that it is necessary for the compressed air which is to be discharged from the nozzle under high pressure to be introduced into the central region of the cross-section of the conduit region. The consequence of this is that at least one suitable pneumatic line must be passed into the central region of the cross-section of the conduit, which means that the at least one pneumatic line is in the flow path of the flock-air mixture and thus, in addition to the pneumatic action of dispersing the flock lumps, can also afford a mechanical dispersing action in the same manner as previous dispersing device involving impact bars against which the flock-air mixture impinges to cause lumps to be dispersed.
In a further preferred feature the pneumatic dispersing device is in the form of an injector nozzle in the form of a tube portion, with the flock-air mixture constituting the respective partial flow flowing through the injector nozzle itself. A pressure fluid under high pressure, more particularly for example compressed air, is fed to the injector nozzle by way of one and preferably a plurality of flow openings which are in the form of feed passages. The pressure fluid can either come from a pressure fluid source which is additionally provided for that purpose, or it can come from a pressure fluid source which in any case is already present for other systems of the machines involved in the present context. The preferably plurality of feed passages in accordance with the invention can be disposed in the outer peripheral region of the flow space of the injector nozzle, through which the flock-air mixture flows.
It will be appreciated that the pneumatic dispersing device or injector nozzle acts in a fluid-mechanics fashion like a fluid or air flow booster. A reduced pressure obtains at the entry or intake side while an increased pressure occurs at the exit or ejection side thereof. The dispersing device or injector nozzle can therefore act like a suction blower arranged at the end of the conduit carrying the respective partial flow of the flock-air mixture, so that, depending on the respective overall length of the conduits, it is possible to forego the inclusion of a further fan or blower in the flock-delivery path.
Further objects, features and advantages of the invention will be apparent from the description hereinafter of a preferred embodiment of the invention.